A Fast Method for Predicting Radio Waves Propagation Over Rough Sea Surfaces

This letter presents a fast method to predict the long distance propagation of radio waves over rough sea surfaces. This method is based on a reasonable setting of the horizontal step for the parabolic equation model with the staircase terrain approach. The critical horizontal range where the effect of sea surface roughness is negligible is determined by analyzing the shadowed roughness reduction factor. A small horizontal step is used in the parabolic equation model when the receiver range is smaller than the critical range, and a large horizontal step is used otherwise. Not only do the propagation factors obtained by the parabolic equation model with nonuniform horizontal steps agree very well with those obtained using the small uniform step, but the computational time for the former is roughly an order of magnitude smaller relative to the latter. In addition, we confirm that the altitudes of minima and maxima of average propagation factor obtained from the parabolic equation model are close to those from the two-ray model as well as the rigorous method of moments.